Attractin (DPPT-L) is a human glycoprotein belonging to a family of proteins called the CUB family of cell adhesion and guidance proteins. Attractin is normally secreted by activated human T lymphocytes and modulates immune cell interactions.
Attractin is an 1198 amino acid protein containing four EGF-like domains along with other domains. Proteins with EGF-like domains typically play a role in extracellular signaling or cellular guidance. For example, purified-serum attractin and recombinant attractin enhance the proliferative response of peripheral blood mononuclear cells (PBMC) to recall antigens such as tetanus toxoid (Duke-Cohan et al., Proc. Nat. Acad. Sci., 95:11336-41, 1998). Attractin causes spreading of adherent monocytes to which lymphocytes attach (Duke-Cohan et al., supra). These adherent cells become the foci for T-lymphocyte clustering, and it is thought that attractin is involved in mediating the interactions between T-cells and macrophages, by influencing binding between the cells, antigen presentation, or by proteolytic modification. In addition attractin has also been identified as being related to the murine mahogany protein with a connection to control of pigmentation and energy metabolism (Tang et al., Proc. Nat. Acad. Sci., 97(11):6025-30, 2000).
Mahogany is a murine protein that is an ortholog of human attractin (Gunn et al., Nature, 398:152, 1999). Murine Mahogany is a transmembrane protein of 1428 amino acids, which contains a single transmembrane domain. The extracellular domain of murine mahogany has homology to attractin. Murine mahogany has been shown to be involved in suppression of obesity (Nagle et al., Nature, 398:148-152, 1999; see also U.S. Pat. No. 6,274,339, which is incorporated herein by reference in its entirety).